Copying material for the photomechanical production of printing plates especially planographic and offset printing plates



United States Patent 3,236,646 COPYING MATERHAL FOR THE PHEPTUME- CHANICAL PRODUCTEON 0F PRHNTENG PLATES ESPECHALLY PLANOGRAPHIC AN 1) OFFSET PRHNTHNG PLATES Hartmut Steppan, Wiesbaden-Dotzheim, and August Rehenstock and Wilhelm Neugebauer, Wieshaden-Biehrich, Germany, assignors, by mesne assignments, to Azoplate ugiorporation, Murray Hill, N.J., a corporation of New ersey No Drawing. Filed Jan. 22, 1962, Ser. No. 167,910 Claims priority, application Germany, .lan. 25, 1961, K 42,721 52 Claims. (Cl. %33) For the photomechanical manufacture of printing plates for planographic and offset printing, light sensitive diazo compounds of higher molecular weight, especially the easily produced condensation products of diphenylamine- 4-diazonium salts and formaldehyde, have found wide use as the light sensitive ingredients of the copying layers. As a carrier for the light sensitive layer, various materials, such as aluminum, zinc, paper and stone are suitable. Up to the present time, the condensation products mentioned above were used in the form of their sulfates, as Well as their metal halide double salts, diazoamino compounds and diazo sulfonates; they were precipitated as such out of the condensation mixtures.

Because of the low light sensitivity of the diazo sulfonates and diazoamino compounds, they are unsuitable for the purpose mentioned above. For copying material, sensitized with metal halide double salts or sulfates of the condensation product, their limited shelf-life is a disadvantage. To make use, for the photomechanical preparation of printing plates, of the good light sensitivity of the metal halide double salts of the condensation products condensed in sulfuric acid from diphenylamine-4-diazonium salts and formaldehyde, a layer of silicate or polymeric carboxylic acids, which attaches itself firmly to the aluminum base, was first applied in a multistep operation, onto the aluminum foil and then the light sensitive coating was applied. By this procedure, the diazo coating is separated from the metallic aluminum by an intermediate layer, andupon exposure under a master-the light decomposition products attach themselves firmly to this intermediate layer and thus to the carrier, resulting in printing plates capable of long runs.

One object of the present invention is the production of a copying material for the photomechanical preparation of printing plates, especially flat and offset printing plates, the light sensitive layer of which comprises polyfunctional diphenylamine-4-diazonium salts, obtained by condensation of formaldehyde with diphenylamine-4-diazonium salts and which, although prepared by a technically simplified procedure, is in no way inferior and in many ways superior to the copying material mentioned above. The copying material according to the invention, which consists of the carrier and the coating adhering thereon, which is made light sensitive by salts prepared by the condensation of diphenylamine-4-diazonium salts with formaldehyde in an acid selected from the group consisting of hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid and trifluoro acetic acid is characterized by the presence of metal salt-free polyfunctional diphenylamine-4-diazonium salts, of the above mentioned kind, as the light sensitive substance and excess phosphoric acid in the copying layer.

The term phosphoric acid as used in the present case is meant to designate ortho phosphoric acid and the acids derived from ortho-phosphoric acid by splitting off water, such as pyrophosphoric acid, polyphosphoric acid and meta-phosphoric acid. When such condensed phosphoric 3,236,646 Patented Feb. 22, 1966 acids are mentioned it is to be understood for definition in the present case, that 1 mole of such an acid is the amount which contains one mole of bound phosphorus. The ortho-phosphoric acid is preferred in the present case, since the salts of this acid are generally easily soluble in Water. I

As excess phosphoric acid is considered the amount of phosphoric acid per mole of diazonium groups, which exceeds 1.5 moles. In this 1.5 moles of phosphoric acid are also included primary phosphate ions of a diazonium phosphate. For instance, according to this definition, an acid phosphate of one of the above mentioned condensation products contains 0.5 mole excess phosphoric acid.

It can be of advantage to use brushed aluminum foils as a carrier for the copying material of this invention. Such copying material is highly light sensitive, has an excellent storageability and the printing plates made therefrom by photomechanical means are extremely durable.

The metal salt-free polyfunctional diazonium salts which may be used as the light sensitive substances for making the copying layer are for instance: nitrates, fiuoro borates, trifluoroaicetates, halides, phosphates or salts of sulfonic acids, which are applied to the carrier with or without the addition of a small amount of a film forming material, but in any case together with excess phosphoric acid. The phosphoric acid contained in the copying layer is of prime importance for the copying layer made according to the invention. It stabilizes the diazonium salt of the coating, ensures the Water conductivity of the non-image areas of the base material after development, and causes or improves the adherence of the exposed coating onto the carrier, provided the excess of phosphoric acid is not too large. For instance, copying layers on brushed aluminum foils, which consist of or contain metal salt-free condensed diazonium salts, have insuthcient storageability in the absence of phosphoric acid. An exception are copying layers containing acid phosphates.

Further, it has been found that copying material of the above described type, in which the light sensitive substance in the copying layer consists of a metal salt-free neutral polyfunctional diazoniurn phosphate, obtained by condensation of diphenylamine-4-diazonium salt with formaldehyde in one of the acids mentioned above, and in which the copying layer contains either no additional or no more than 0.5 mole additional phosphoric acid per role of diazonium groups, aside from the primary phosphate ions derived from the neutral phosphate, also gives a printing material capable of producing a large amount of Well defined copies.

An equivalent copying material is one in which the light sensitive substance in the copying layer consists of metal salt-free polyfunctional diazonium salts obtained by condensation of diphenylamine-4-diazonium salt with formaldehyde in an acid selected from the groups consisting of hydrofluoric acid, hydrochloric acid, hydro- 'bromic acid, sulfuric acid and trifiuoro acetic acid, and in which the copying layer contains from 0.05 to 1.5 moles of phosphoric acid per mole of diazonium groups.

Aside from the above mentioned brushed aluminum foils, electrolytically roughened aluminum, paper suitable for printing plates and superficially saponified cellulose acetate foils can be used as a carrier for the manufacture of the copying material of this invention. When using the salts in the presence of excess phosphoric acid, all give copying material of excellent shelf life and periormance.

For the manufacture of copying layers according to the invention condensation products are used, which are prepared at room temperature or at a slightly elevated temperature, from unsubstituted or substituted diphenylamine-4-diazonium salts and formaldehyde in hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid or trifluoro acetic acid and are obtained as metal salt-free salts. As substituted or unsubstituted diphenylamine-4-diazonium salts which are used as starting material for the production of the condensation products of the invention there are cited for example the diazotisation products at the following amino-compounds. 4-amino-diphenylamine 4-amino-3-methoxy-diphenylamine 4-amino-2-methoxy-diphenylamine 4-amino-2-methoxy-diphenylamine 4'-amino-4-'methoxy-diphenylamine 4-amino-3-methyl-diphenylamine 4-amino-3-ethyl-diphenylamine 4-amino-3-methyl-diphenylamine 4'amino-4-methyl-diphenylamine 4-amino-3-et.hoxy-diphenylamine 4-amino-3-hexyloxy-diphenylamine 4'-a mino-6-methoxy-3-methyl-diphenylamine 4-amino-6-methoxy-3-methyl-diphenylamine 4-amino-3,3-dimethyl-diphenylamine 3'-chloro-4-amino-diphenylamine 4-amino-2,5-diethoxy-diphenylamine 4-amino-4-n-b utyloxy-diphenylamine 4'-amino-4,3-dimethoxy-diphenylamine 4-amino-diphenylamine-Z-carboxylic acid 4-amino-diphenylamine-2'-carboxylic acid For the condensation, in general, a molar ratio of diazonium salt to formaldehyde of 1:1 is used. The formaldehyde can be used as a concentrated aqueous solution. However, it is preferred to use gaseous formaldehyde or polymers of formaldehyde which are capable of spliting off formaldehyde under reaction conditions. Useful products, however, are also obtained if the molar ratio employed is smaller or larger than 1:1, but no larger than 2:1. To facilitate the isolation of the condensation products in solid form, the amount of the acid used as a condensation medium should be as small as possible.

Depending on the acid used for condensation, products of different degrees of condensation are obtained. A qualitative evaluation 'of the degree of condensation is obtained by means of paper chromatography (Schleicher & Schuell 2043b; butanol/ glacial acetic acid/water 40:10:50). The higher the degree of condensation, the smaller the R value of the product. Thus, products with a higher R -value and a lower degree of condensation are obtained, for instance, in hydrohalide acids than in sulfuric acid.

The salts of the condensation products are produced or precipitated according to different methods depending upon the condensation medium used.

When a substituted or unsubstituted diphenylamine-4- diazonium chloride or bromide is condensed with formaldehyde in hydrofluoric acid, hydrochloric acid or hydrobromic acid, the condensation products can be isolated without decomposition by evaporating the condensation mixture to dryness at a temperature not exceeding 70 C., preferably under vacuum. Since condensation products of diphenylamine-4-diazonium salts and formaldehyde can form acid salts, in excess acid, of the general formula ArN X-HX, in which Ar is the condensed diphenylamine unit, acid halides or mixtures of acid and neutral halides of the condensation product of the formula ArN X'nHX (n=1) are obtained as the residue of evaporation, depending on the acid used and on the conditions of evaporation.

Salts of condensation products, the anions of which are derived from volatile acids, are transformed to acid phosphates of the composition ArN H PO -H PO by dissolving them in strong phosphoric acid, blowing off the volatile acid, for instance hydrochloric acid, by means of a stream of dry gas and precipitating the desired product with organic solvents.

by dissolving the acid phosphates, treating the solutions with weakly basic ion-exchangers and evaporating the solvent.

If the condensation is effected in sulfuric acid, the chlorides or bromides of the condensation products are prepared as follows: The condensation mixture is diluted with methanol, the calculated amount of chloride or bromide ions is added and, after removal of the sulfate ions, for example by treating with calcium carbonate, the mixture is evaporated to dryness.

Ortho-phosphates, halides, fluorobora tes, and trifluoroacetates of the condensation products and the salts of sulfonic acids are products having good storageability, which are easily soluble in mixtures of water with waterrniscible solvents. With the exception of the phosphates, the salts are also easily soluble in certain organic solvents, also in the presence of ortho-phosphoric acid and, therefore, can be combined with a number of additives soluble only in organic solvents. The ortho-phosphates of the condensation products are especially and more generally soluble in water. Salts of a low degree of condensation are usually easier to dissolve than those of a high degree of condensation.

For the manufacture of copying layers according to the invention, the salt of the condensation product is dissolved in water or mixtures of water with water-miscible solvents or mixtures of the solvents, then usually the phosphoric acid is added and the carrier material is coated in the usual manner, for example by wiping on or whirling on the solution. As compared with aqueous solutions, the use of solutions of the condensation products in organic solvents has the advantage of yielding more uniform coatings.

The optimum concentration of the diazo compound in the coating solution is dependent upon the coating method, the coating conditions, and the carrier material. Usually, good copying layers are obtained if the concentration of diazonium salt in the coating solution is between 0.001 and 10% by weight. Higher concentrations are possible. However, no further advantage is usually obtained. The preferred range is between 0.02 and 5% by weight. The amount of the condensation product used depends somewhat on the base material used. For aluminum bases, the lower values in the preferred range are used e.g. between 0.05 and 0.5% by weight. It a paper base material is used generally more condensation product is used in the light sensitive coating e.g. from. 0.3 to 5 percent by weight. The optimum amount of phosphoric acid required for the stabilization of the coating also depends on the carrier material. On brushed aluminum foils, coatings of good shelf life are obtained it 1.05 to 5 preferably 1.5 to 3 moles of phosphoric acid are used per mole of diazonium group. When neutral or acid phosphates of the condensation products are used, 0.05 to 4 or 0.01 to 3 moles of phosphoric acid per mole of diazonium group are added. If a paper carrier is used usually a larger amount of phosphoric acid is added e.g. from 2 to 30 preferably from 6 to 15 moles. In such a case part of the phosphoric acid may be replaced by another acid of low volatility e.g. sulfuric acid or arsenic acid. In this case the term excess phosphoric acid should also include such mixture of acids.

To the copying layers according to the invention additives commonly used in conjunction with diazo reproduction material, such as oxidation inhibitors, film formers and others can be added.

The preparation of the printing plates from the copying material of this invention is effected in the usual manner. The copying material is exposed under a negative and, after developing with, for example, water or aqueous solutions of gum arabic or emulsion lacquer developers, for example those described in US. Patent No. 2,754,279, a positive printing plate is obtained which accepts greasy ink very readily and is capable of long runs. Printing plates of even better quality are obtained if the use of aqueous developers prior to lacquering is omitted and the copying layer which has been exposed under a master is wiped instead with a water-miscible solvent, preferably ethylenegycol, polyglycol or glycerine, then the lacquer is applied and finally it is treated with aqueous compositions.

If the printing plates are not used immediately after their preparation, it is advisable to gum them,

In the following examples, parts by weight correspond to parts by volume as grams to millimeters.

EXAMPLES (1) A brushed aluminum foil is coated with a solution containing 0.17 part by weight of a condensation product of 3-methoxy-diphenylamine-4-diazonium chloride and formaldehyde, condensed in 80% sulfuric acid and precipitated in the form of the chloride, and 0.13 part by weight of 85% phosphoric acid in a solvent mixture consisting of 8 parts by volume of water, 55 parts by volume of ethyleneglycol monomethylether and 37 parts by volume of dimethylformamide. The coated solution is dried at temperatures up to 100 C.

The copying layer, which has a good shelf life in the unexposed state, is exposed for to 60 seconds under a carbon arc, conventional in the trade, for example an 18 ampere lamp at a distance of about 60 cm.

The exposed material is developed by wiping with water or an aqueous 14% gum arabic solution, which contains 0.06% of phosphoric acid. The printing master can be put on a printing machine immediately and is capable of reproducing a large number of perfect copies. The plate life can be considerably increased if a lacquer is applied, for instance a lacquer of the kind described in U.S. Patent No. 2,754,279.

Instead of the brushed aluminum, an electrolytically grained aluminum foil can be used. However, in this case, it is advisable to increase the concentration of the phosphoric acid and of the diazo in the coating solution about four times.

For the preparation of the condensation product of 3-methoxy-diphenylaminet-diazonium chloride and formaldehyde, 10.45 parts by weight of B-methoxy-diphenylamine-4-diazonium chloride are introduced, with stirring, into 25.6 parts by volume of 78 percent (by weight) sulfuric acid. Within 4 hours, 1.21 parts by weight of paraformaldehyde are added in portions to this mixture. Subsequently, the mixture is heated for two hours to a temperature of 40 C. and then left standing for 12 hours at room temperature. The mixture is then poured into 200 parts by volume of saturated aqueous barium chloride solution, and further saturated barium chloride solution is added until no more barium or sulfate ions are detectable in the solution. Barium sulfate is separated, the solution is filtered over charcoal, and then evaporated to ryness under vacuum at a temperature not exceeding 60 C.

8.5 parts by weight are obtained of a mixture of approximately equal parts of the acid and the neutral chlorides of the condensation product.

With identical results and in the same manner, the bromide of the product obtained by condensation in sulfuric acid which is analogously prepared can be used for making the copying layer.

Copying material of good quality is also obtained by using, instead of the salts mentioned above, equal quantities of the chloride or the bromide of a condensation product of 3-ethoxy-diphenylamine and formaldehyde prepared analogously.

The chlorides and bromides of the condensation products made according to this method are obtained in the form of brown or brownish-green solids. They have good shelf life and are easy to ship (2) A brushed aluminum foil is coated with a solution consisting of 0.1 part by weight of a condensation product of diphenylamine-4-diazonium sulfate and formaldehyde, prepared in sulfuric acid and precipitated as the chloride, and 0.12 part by Weight of 85% phosphoric acid in admixture with 16 parts by volume of water, 110 parts by volume of ethyleneglycol monomethylether and 74 parts by volume of dimethyl-formamide.

Instead of the chloride, the bromide of the condensation product can be used for making the copying layer with similar results.

The processing of the coating for making the printing plate is performed as described in Example 1.

To prepare the diazonium chloride, 23 parts by weight of diphenylamine-4-diazonium sulfate are stirred into parts by volume of sulfuric acid (78%) during 1 hour, and then 2.4 parts by Weight of paraformaldehyde are added within 4 hours. The mixture is stirred for 2 hours at 40 C. and then left standing for 12 hours at room temperature.

The chloride and the bromide of the condensation product are prepared analogously to the method described in Example 1.

(3) A brushed aluminum foil is coated with a solution of 0.14 part by weight of a condensation product of diphenylamine-4-diazonium chloride and formaldehyde prepared in hydrochloric acid and precipitated as the chloride, and 0.13 part by weight of 85% phosphoric acid in a mixture consisting of 8 parts by volume of water, parts by volume of ethyleneglycol monomethylether and 37 parts by volume of dimethylforamide. The printing form is made as described in Example 1.

A copying layer of equal performance is obtained if, instead of 0.14 part by weight of the above mentioned condensation product, 0.16 part by weight of a condensation product of diphenylamine-4-diazonium chloride and formaldehyde, prepared in 66% hydrobromic acid and precipitated as the bromide, or 0.11 part by weight of a product made from diphenylamine-4-diazonium chloride and formaldehyde by condensation in 40% hydrofluoric acid, are dissolved and coated under identical conditions.

The condensation products are prepared as follows:

Condensation in hydrochloric acid 46 parts by weight of diphenylaminet-diazonium chloride and 6 parts by weight of paraformaldehyde are stirred in 200 parts by volume of concentrated hydrochloric acid, first for 8 hours at a temperature of 50 C. and then for 12 hours at room temperature. The mixture is then evaporated to dryness under vacuum at a bath temperature of 50 to 55 C. The residue is a mixture of neutral and acid chlorides of the condensation product.

Condensation inv hydrobromic acid 138 parts by Weight of diphenylamine-4-diazonium chloride and 18 parts by Weight of paraformaldehyde are heated in 300 parts by volume of 66% hydrobromic acid for 7 hours to a temperature of 50 C. The mixture is then evaporated to dryness under vacuum at a maximum temperature of 70 C. The condensation product is obtained in the form of an acid bromide.

Condensation in hydrofluoric acid 23.15 parts by Weight of diphenylamine-4-diazonium chloride and 3.3 parts by weight of paraformaldehyde are heated in 50 parts by volume of 40% hydrofluoric acid for 20 hours to a temperature of 40 C. and for 16 hours to a temperature of 50 C. The solution is then concentrated at 50 C., by blowing a stream of air through it, and dried completely under vacuum over potassium hydroxide. A product is obtained which contains one fiuoride ion and one chloride ion per diazonium group.

(4) The preparation and use of the coating solution is as in Example 1, except that for preparing the solution, equimolecular amounts of trifiuoroacetate, fiuoroborate or 1,8-dinitronaphthalene-3,6-disulfonate of a condensation product are used which was prepared by condensing diphenylamine-4-diazonium salt and formaldehyde in sulfuric acid, under the conditions stated in Example 2. The printing plate is made as described in the examples above.

Manufacture of the salts T riflur0acetare.--The chlorides of the condensation products are dissolved in water and, upon addition of trifluoroacetic acid, the raw trifiuoroacetate is precipitated as an oil. Through repeated dissolving of the oil in water and reprecipitation with trifluoroacetic acid it is freed of chloride. The oily trifluoroacetate is dried under vacuum at elevated temperatures and is obtained in solid form by treating with ethyl acetate.

Flu0r0b0rate.The acid condensation mixtures are diluted with water and, upon addition of fluoboric acid, the fiuoroborate is precipitated. It is filtered off and dried.

1,8 dinitronaphthalene-3,6-disulf0nate.Raw condensation mixtures are diluted with water and mixed with aqueous solutions of the sulfonic acid or alkali salts of the sulfonic acid. The precipitate is separated off and dried.

A brushed aluminum foil is coated with a solution containing 0.15 part by weight of a condensation product of diphenylamine-4-diazonium sulfate and formaldehyde, condensed in sulfuric acid and precipitated in the form of the acid phosphate, and 0.045 part by weight of 85% phosphoric acid in a mixture of 16 parts by volume of water, 110 parts by volume of ethyleneglycol monomethylether and 74 parts by volume of dimethyl formamide. The coated solution is dried at a temperature of about 100 C. The copying material has a good light sensitivity and shelf life and is converted into a printing plate as described in the foregoing examples.

Instead of using the compound made in sulfuric acid, a condensation product obtained by condensation in a hydrohalide acid and precipitated as an acid phosphate can be used for making the copying layer.

The acid phosphates required can be obtained as follows:

In 16 to 24 parts by volume of 85% phosphoric acid are dissolved 8 parts by weight of a chloride of a condensation product, obtained by condensation of diphenylamine-4-diazonium salt with formaldehyde in sulfuric or hydrohalide acid. A dry stream of gas is passed through the mixture until chloride ions can no longer be detected. The mixture is then diluted with methanol and poured into isopropanol, whereupon the acid phosphate of the condensation product is precipitated, separated and dried.

(6) A base paper prepared in accordance with the teaching of US. patent specification No. 2,778,735 is coated with a solution containing, dissolved in 100 parts by volume of water, 3.7 parts by weight of 85 percent phosphoric acid and 1.31 parts by weight of a condensation product which was prepared by condensing 3-methoxy-diphenylamine-4-diazonium chloride and formaldehyde in sulfuric acid and obtained in the form of the chloride by adding chloride ions and removing the sulfuric acid.

The diazonium salt required is prepared as described in Example 1.

After an exposure of 60 to 120 seconds under a negative master, using the carbon are lamp mentioned in Example 1 as a light source, and wiping over with water or dilute gum arabic solution, a positive printing plate is obtained from which long runs can be obtained. The reproduction material mentioned in the present example has a very good shelf life in the unexposed state.

A reproduction material of good performance is also obtained when the base paper mentioned above is coated with a solution containing 1.6 parts by weight of the condensation product described below and 7 parts by weight of 85 percent phosphoric acid dissolved in 100 parts by volume of water.

The condensation product is prepared as follows: 23.4 parts by weight of 4-methoxy-diphenylamine-4-diazonium sulfate are condensed with 1.67 parts by weight of paraformaldehyde in parts by volume of 78 percent sulfuric acid, first for one hour at C. and then for 12 hours at room temperature. As described above, the sulfate ions are precipitated by adding barium chloride to the solution, the barium sulfate is separated by filtration, and the filtrate is evaporated to dryness. 15 parts by weight are obtained of a mixture of the acid and the neutral chlorides of the condensation product.

(7) A brushed aluminum foil is coated with a solution containing 0.13 part by weight of a sulfate of a condensation product of a diphenylamine-4-diazonium salt and formaldehyde, prepared in sulfuric acid, and 0.11 part by weight of 85% phosphoric acid in 8 parts by volume of water, parts by volume of ethyleneglycol-monomethylether and 37 parts by volume of dimethylformamide.

By exposure of the dry copying material under a master, wiping over the exposed layer with ethyleneglycol monomethylether and lacquering, a printing plate is obtained from which can be obtained a large number of flawless copies.

The sulfate of the high molecular weight condensation product, prepared in sulfuric acid, can be obtained for example according to the teachings of U8. Patent 2,679,498.

(8) A superficially saponified cellulose acetate foil is coated with a solution containing 1 part by weight of a condensation product of diphenylamine-4-diazonium sulfate and formaldehyde, prepared in 96% sulfuric acid and precipitated in the form of the sulfate, following the method described in US. Patent No. 2,679,498, and 2 parts by weight of phosphoric acid in 100 ml. of water. After drying and exposure under a master, the copying material which has a good shelf life, is developed by wiping with water, and is then inked up with greasy printing ink. A large number of flawless prints are obtained from this printing plate.

(9) A brushed aluminum foil is coated, on a plate whirler, with a solution containing 0.1 part by weight of a condensation product prepared from 4-methyl-diphenylamine-4'-diazonium sulfate and formaldehyde, by condensation in sulfuric acid and obtained in the form of the metal salt-free chloride, and 0.08 part by weight of 85 phosphoric acid, dissolved in a mixture of 8 parts by volume of water, 55 parts by volume of ethyleneglycol monomethylether, and 37 parts by volume of dimethylformamide.

The copying material thus obtained is converted into a printing plate from which long runs can be obtained.

The condensation product mentioned above is prepared as follows:

20 parts by weight of 4-methyl-diphenylamine-4-diazonium sulfate are introduced into a solution containing 1.96 parts by weight of paraformaldehyde in 42 parts by volume of 78 percent sulfuric acid. The mixture is heated to 40 C. for minutes and then left standing overnight at room temperature. Sufficient barium chloride solution is added until neither sulfate nor barium ions can be detected in the solution, the barium sulfate is separated, and the residue is evaporated to dryness.

Similar results are obtained if, for sensitizing the carrier, the acid phosphate of the condensation product is used, which is obtained from the chloride by dissolving the chloride in phosphoric acid removing the hydrochloric acid by passing a stream of gas, e.g. air, through the solution, and precipitating by means of organic solvents.

For example, a solution containing 0.14 part by weight of this condensation product, dissolved in a mixture consisting of 8 parts by volume of water, 54 parts by volume of ethyleneglycol monomethylether, and 37 parts by volume of dimethylformamide, may be used for coating.

A reproduction material of equal performance is obtained if, instead of the chloride or the phosphate of the condensation product mentioned above equal amounts of the chlorides or phosphates of the condensation products prepared analogously from 3-methyl-diphenylaminel-diazonium salt or, respectively 3-methyl-diphenylamine-4'- diaz-onium salt, and formaldehyde are used for the prepa ration of the coating solution.

Presensitized brushed aluminum foils of equal quality are obtained if, instead of the compounds mentioned above, a sensitizing solution is used containing 0.15 part by weight of the chloride of the condensation product of 4-methoxy-diphenylamine-4'-diazonium sulfate and formaldehyde described in Example 6 and 0.115 part by weight of 85 percent phosphoric acid in a mixture consisting of 8 parts by volume of water, 55 parts by volume of ethyleneglycol monomethylether, and 37 parts by volume of dimethylformamide.

(10) A paper base, described in detail in US. Patent No. 2,778,735, is coated with a solution containing 2 parts by weight of a condensation product of diphenylamine-4- diazoniumphosphate-Z-carboxylic acid and formaldehyde, prepared in sulfuric acid and precipitated in the form of its bisulfate and 5 parts by weight of 85 percent phosphoric acid in 100 parts by volume of water. A copying material of good shelf life is thus obtained which, after exposure under a master and subsequent treatment with water, yields a printing plate from which a large number of flawless prints can be made.

The bisulfate of the condensation product is prepared as follows:

parts by weight of diphenylamine-4-diazoniurn phosphate-Z-carboxylic acid and 1.33 parts by weight of paraformaldehyde are successively introduced into 28.4 parts by volume of 78 percent sulfuric acid. The reaction mixture is heated for 90 minutes to 40 (3., left standing overnight and is then poured into 500 parts by volume of isopropanol. The mixture is heated for 45 minutes at 40 C., the easily filterable precipitate is removed by suction filtration, the filtrate is washed with isopropanol, and the residue is dried under vacuum at 40 C.

A copying material of equal quality is obtained if the paper base is sensitized with the bisulfate of a condensation product prepared, by the same method, from diphenylaminel-diazonium phosphate 2'-carboxylic acid.

(11) A brushed aluminum foil is coated in the usual manner with a solution containing 0.15 part by weight of a condensation product of diphenylamine-4-diazonium chloride and paraformaldehyde, prepared in concentrated hydrochloric acid and precipitated in the form of the acid chloride, and 0.5 part by volume of 0.1 molar phosphoric acid, dissolved in a mixture consisting of 55 parts by volume of ethyleneglycol monomethylether, 37 parts by volume of dimethylformamide, and 7.5 parts by volume of water. By exposure under a master and wiping over with an aqueous gum arabic solution or treatment with an emulsion lacquer, e.g. the one described in US. patent specification No. 2,754,279, a printing plate is obtained from which a large number of flawless prints can be obtained.

(12) 0.145 part by weight of a condensation product prepared by the condensation of diphenylamine-4-diazonium-chloride and formaldehyde in hydrochloric acid and isolated in the form of the acid chloride, and 0.111 part by weight of pyrophosphoric acid are dissolved in a mixture consisting of 8 parts by volume of water, 55 parts by volume of ethyleneglycol monomethylether, and 37 parts by volume of dimethylformamide. The solution thus obtained is used for coating a brushed aluminum foil in the usual manner. After exposure under a negative master, wiping over with an aqueous gum arabic solution, and subsequent inking up with greasy ink, a positive printing plate is obtained which is capable of long runs. The unexposed reproduction material has a very good shelf-life.

(13) A base paper manufactured in accordance with US. patent specification No. 2,778,735 is coated with a solution containing 2.3 parts by Weight of a condensation product prepared from 3-methoxy-diphenylamine-4-diazonium chloride and formaldehyde in hydrochloric acid and precipitated in the form of the chloride, 8 parts by weight of percent phosphoric acid and 2. parts by weight of concentrated sulfuric acid in parts by volume of Water. After exposure under a negative master and wiping over with water or a dilute aqueous solution of gum arabic, a positive printing plate is obtained from which long runs can be obtained. The reproduction ma terial prepared in this manner has a very good shelf life in the unexposed state.

The diazonium chloride required is obtained as follows: 10.45 parts by weight of 3-methoxy-diphenylamine- 4-diazonium chloride are mixed with 1.21 parts by Weight of paraformaldehyde. The mixture is introduced into 20 parts by volume of concentrated hydrochloric acid and agitated, first for one hour at 40 C. and then for 20 hours at room temperature. Subsequently, the reaction mixture is evaporated to dryness under vacuum and at a temperature of 40 C. 11 parts by weight of a mixture are obtained consisting to about equal parts of the acid and the neutral chlorides of the condensation product. A reproduction material of equally good quality is obtained if, instead of the condensation product mentioned above, equivalent quantities of the chloride of a condensation product are used which is prepared analogously from 2-methoxy-diphenylamine-4-diazonium salt or 2- methoxy-diphenylamine-4-diazonium salt and formaldehyde.

(14) The method described in Example 11 is followed, but for coating the brushed aluminum support a solution is used which contains 0.135 part by weight of the neutral polyfunctional diazonium phosphate described below and 0.008 part by weight of 85 percent phosphoric acid in a mixture consisting of 8 parts by volume of water, 55 parts by volume of ethyleneglycol monomethylether, and 37 parts by volume of dimethyl-formamide.

For the preparation of the neutral diazonium. phosphate, diphenylamine-4-diazonium chloride is condensed with fomaldehyde in hydrochloric acid as described in Example 3. The chloride of the condensation product is then converted into the acid phosphate by the method described in Example 5. The acid phosphate is dissolved in water and the solution is treated with weakly basic ion exchanger, such as the one marketed by Merck, Darmstadt (Germany), under the designation Ionenaustauscher II, until a pH-value of 6 has been reached. Subsequently, the solvent is completely evaporated under vacuum at a temperature of 40 to 50 C.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. A presensitized printing plate comprising a base material having a coating thereon comprising at least one metal salt-free polyfunctional condensation product of a diphenylamine-4-diazonium salt with formaldehyde condensed in an acid selected from the group consisting of hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, and trifiuoroacetic acid, and added excess phosphoric acid.

2. A presensitized printing plate according to claim 1 in which the excess phosphoric acid is up to 30 moles of phosphoric acid per each mole of diazonium groups.

3. A presensitized printing plate according to claim 1 in which the metal salt-free polyfunctional condensation product is a phosphate salt.

4. A presensitized printing plate comprising a base material having a coating thereon comprising at least one neutral metal salt-free polyfunctional diazonium phosphate condensation product of a diphenylamine-4-diazonium salt with formaldehyde, containing, in addition to the phosphate ions of the neutral diazonium phosphate, no more than about 0.5 mole of added phosphoric acid per mole of diazonium groups.

5. A presensitized printing plate comprising a base material having a coating thereon comprising at least one metal salt-free polyfunctional condensation product of a diphenylamine-4-diazonium salt with formaldehyde condensed in an acid selected from the group consisting of hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, and trifiuoroacetic acid, and added phosphoric acid in an amount not exceeding about 1.5 moles per mole of diazonium groups.

6. A presensitized printing plate according to claim 1, in which the condensation product is employed in the form of a salt of the formula AI'N2H2PO4 H3PO4 in which Ar is a condensed diphenylamine group.

7. A presensitized printing plate according to claim 1 in which the condensation product is employed in the form of a salt of the formula ArN X-nHX in which Ar is a condensed diphenylamine group, X is selected from the group consisting of fluorine, chlorine, and bromine, and n represents a number from O to 1.

8. A presensitized printing plate according to claim 1 in which the condensation product is employed in the form of a fluoroborate salt.

9. A presensitized printing plate according to claim 1 in which the condensation product is employed in the form of a trifluoroacetate salt.

10. A presensitized printing plate according to claim 1 in which the condensation product is employed in the form of a salt of an organic sulfonic acid.

11. A presensitized printing plate according to claim 1 in which the condensation product is employed in the form of a sulfate salt.

12. A presensitized printing plate according to claim 1 in which the condensation product is employed in the form of a bisulfate salt.

13. A presensitized printing plate according to claim 1 in which the condensation product is of a diphenylamine- 4-diazonium phosphate with formaldehyde.

14. A presensitized printing plate according to claim 1 in which the condensation product is of a diphenylamine- 4-diazonium chloride with formaldehyde.

15. A presensitized printing plate according to claim 1 in which the condensation product is of a diphenylamine- 4-diazonium sulfate with formaldehyde.

16. A presensitized printing plate according to claim 1 in which the condensation product is of a 3-methoxy-diphenylaminel-diazonium salt with formaldehyde.

17. A presensitized printing plate according to claim 1 in which the condensation product is of a 4-methyl-diphenylamine-4-diazonium salt with formaldehyde.

18. A presensitized printing plate according to claim 1 in which the condensation product is of a 4-methoxy-diphenylamine-4-diazonium salt with formaldehyde.

19. A presensitized printing plate according to claim 1 in which the condensation product is of a 3-ethoxy-diphenylamine-4-diazonium salt with formaldehyde.

20. A presensitized printing plate according to claim 1 in which the condensation product is of a 2-methoxy-diphenylamine-4-diazonium salt with formaldehyde.

21. A presensitized printing plate according to claim 1 in which the condensation product is of a 3-methyl-diphenylamine-4-diazouium salt with formaldehyde.

22. A presensitized printing plate according to claim 1 in which the condensation product is of a 3-methyl-diphenylamine-4'-diazonium salt with formaldehyde.

23. A presensitized printing plate according to claim 1 in which the condensation product is of a 2-carboxy-diphenylamine-4-diazonium salt with formaldehyde.

24. A presensitized printing plate according to claim 1 in which the base material is aluminum.

25. A presensitized printing plate according to claim 1 in which the base material is paper.

26. A presensitized printing plate according to claim 24 in which the aluminum base carries a coating containing from 1.05 to 5 moles of phosphoric acid per each mole of diazonium groups.

27. A presensitized printing plate according to claim 25 in which the paper base carries a coating containing from 2 to 30 moles of phosphoric acid per each mole of diazonium groups.

28. A process for developing a printing plate which comprises exposing a supported layer to light under a master and treating the exposed layer with a developer, the layer comprising at least one metal saltree polyfunctional condensation product of a diphenylamine-4-diazonium salt with formaldehyde condensed in an acid selected from the group consisting of hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, and trifiuoroacetic acid, and added excess phosphoric acid.

29. A process according to claim 28 in which the metal salt-free polyfunctional condensation product is a phosphate salt.

30. A process for developing a printing plate which comprises exposing a supported layer to light under a master and treating the exposed layer with a developer, the layer comprising at least one neutral metal salt-free polyfunctional diazonium phosphate condensation product of a diphenylamine-4-diazonium salt with formaldehyde, containing, in addition to the phosphate ions of the neu tral diazonium phosphate, no more than about 0.5 mole of phosphoric acid per mole of added diazonium groups.

31. A process for developing a printing plate which comprises exposing a supported layer to light under a master and treating the exposed layer with a developer, the layer comprising at least one metal salt-free polyfunctional condensation product of a diphenylamine-4-diazonium salt with formaldehyde condensed in an acid selected from the group consisting of hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, and trifluoroacetic acid, and added phosphoric acid in an amount not exceeding about 1.5 moles per mole of diazonium groups.

32. A process according to claim 28 in which the condensation product is employed in the form of a salt of the formula A1 N2H2PO4 H3PO4 in which Ar is a condensed diphenylamine group.

33. A process according to claim 28 in which the condensation product is employed in the form of a salt of the formula ArN2X HX in which Ar is a condensed diphenylamine group, X is selected from the group consisting of fluorine, chlorine and bromine, and n is a number from O to 1.

34. A process according to claim 28 in which the condensation pro-duct is employed in the form of a fluoroborate salt.

35. A process according to claim 28 in which the condensation product is employed in the form of a trifluoroacetate salt.

36. A process according to claim 28 in which the condensation product is employed in the form of a salt of an organic sulfonic acid.

37. A process according to claim 28 in which the condelnsation product is employed in the form of a sulfate sa t.

38. A process according to claim 28 in which the condelnsation product is employed in the form of a bisulfate sat.

39. A process according to claim 28 in which the condensation product is of a diphenylamine-4-diazonium phosphate with formaldehyde.

40. A process according to claim 28 in which the condensation product is of a diphenylamine-4-diazonium chloride with formaldehyde.

41. A process according to claim 28 in which the condensation product is of a diphenylamine-4-diazonium sulfate with formaldehyde.

42. A process according to claim 28 in which the condensation product is of a 3-methoxy-diphenylamine-4-diazonium salt with formaldehyde.

43. A process according to claim 28 in which the condensationfproduct is of a 4-methyl-diphenylamine-4-diazonium salt with formaldehyde.

44. A process according to claim 28 in which the con densation product is of a 4-methoxy-diphenylamine-4'-diazonium salt with formaldehyde.

45. A process according to claim 28 in which the condensation product is of a 3-ethoxy-diphenylamine-4-diazonium salt with formaldehyde.

46. A process according to claim 28 in which the condensation product is of a Z-methoxy-diphenylamine-4-diazonium salt with formaldehyde.

47. A process according to claim 28 in which the condensation product is of a 3-methyl-diphenylamine-4-diazonium salt with formaldehyde.

48. A process according to claim 28 in which the condensation product is of a 3-methyl-diphenylamine-4-diazonium salt with formaldehyde.

49. A process according to claim 28 in which the condensation product is of 2-carboxy-diphenylamine-4-diazonium salt with formaldehyde.

50. A process according to claim 28 in which the support is aluminum.

51. A presensitized printing plate comprising a base material having a coating thereon comprising at least one polyfunctional metal salt-free condensation product of a diphenylamine-4-diazonium salt with formaldehyde condensed in an acid selected from the group consisting of hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, and trifluoroacetic acid, and at least 0.05 mole of added phosphoric acid per mole of diazonium groups.

52. A process for developing a printing plate which comprises exposing a supported layer to light under a master and treating the exposed layer with a developer, the layer comprising at least one polyfunctional metal salt-free condensation product of a diphenylamine-4-diazonium salt with formaldehyde condensed in an acid selected from the group consisting of hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, and trifluoroacetic acid, and at least 0.05 mole of added phosphoric acid per mole of diazonium groups.

References Cited by the Examiner UNITED STATES PATENTS 2,266,229 12/1941 May 260-141 2,679,498 5/1954 Seven et al 96-33 X 2,739,889 3/1956 Neugebauer et al 96-33 2,923,703 2/1960 Bruni 96-91 X 2,937,085 5/ 1960 Seven et al 96-75 X FOREIGN PATENTS 698,040 10/ 1953 Great Britain.

OTHER REFERENCES Saunders: The Aromatic Diazo Compounds, Edward Arnold & Co., London, 1949, p. 76.

NORMAN G. TORCHIN, Primary Examiner.

PHILIP E. MANGAN, Examiner. 

28. A PROCESS FOR DEVELOPING A PRINTING PLATE WHICH COMPRISES EXPOSING A SUPPORTED LAYER TO LIGHT UNDER A MASTER AND TREATING THE EXPOSED LAYER WITH A DEVELOPER, THE LAYER COMPRISING AT LEAST ONE METAL SALT-FREE POLYFUNCTIONAL CONDENSATION PRODUCT OF A DIPHENYLAMINE-4-DIAZONIUM SALT WITH FORMALDEHYDE CONDENSED IN AN ACID SELECTED FROM THE GROUP CONSISTING OF HYDROFLUORIC ACID, HYDROCHLORIC ACID, HYDROBROMIC ACID, SULFURIC ACID, AND TRIFLUOROACETIC ACID, AND ADDED EXCESS PHOSPHORIC ACID. 